A digital video coding method for encoding video frames and outputting a bit stream including picture headers is provided. The digital video coding method includes the steps of identifying what is changed in a coding type between a previous frame and a current frame, and performing a predetermined bitwise logical operation with respect to a value of an indicator field of the previous frame and a bit value, wherein the bit value is determined according to the kind of change in a coding type which is identified in the above step and the indicator field is a predetermined field for indicating whether the coding type has been changed, and determining a result value of the logical operation as a value of an indicator field of the current frame. In the digital video coding method, when encoding a current frame, a value of a group of block frame identifier (GFID) field of the current frame is determined by performing a bitwise logical operation with respect to a value of a GFID field of a previous frame and a bit value representing information on the kind of change in a coding type, and the determined value is embedded in the current frame. Therefore, even if a picture header of a current picture frame is lost, the kind of change in a coding type can be estimated based on the values of GFID fields of the current and previous frames during decoding. Consequently, decoding can be performed using accurate picture header information.
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1. A digital video coding method for encoding video frames and outputting a bit stream including picture headers, the digital video coding method comprising the steps of: (a) identifying what is changed in a coding type between a previous frame and a current frame; and (b) performing a predetermined bitwise logical operation with respect to a value of an indicator field of the previous frame and a bit value, wherein the bit value is determined according to what is changed in the coding type which is identified in the step (a) and the indicator field is a predetermined field for indicating whether the coding type has been changed, and determining a result value of the logical operation as a value of an indicator field of the current frame.
2. The digital video coding method of claim 1 , wherein the indicator field is a group-of-block frame identifier (GFID) field which is defined by an H.263 standard.
3. The digital video coding method of claim 1 , wherein the bitwise logical operation is an exclusive OR operation.
4. The digital video coding method of claim 1 , wherein the bit value has a different value according to a first case in which a rounding type changes, a second case in which an intra frame is changed into an inter frame or an inter frame is changed into an intra frame, and a third case in which a coding type change other than the former two cases occurs.
5. The digital video coding method of claim 4 , wherein the third case includes a change in an annex which is a detailed appendix defining an optional coding method in view of a digital video coding related standard.
6. The digital video coding method of claim 5 , further comprising the step of setting update full extended picture type (UFEP) fields, which are defined by an H.263 standard, to 001 , with respect to the current frame, in which the change in the coding type occurs, and a next frame, when the change in the coding type falls under the third case.
7. The digital video coding method of claim 4 , further comprising the step of setting update full extended picture type (UFEP) fields, which are defined by an H.263 standard, to 001 , with respect to the current frame, in which the change in the coding type occurs, and a next frame, when the change in the coding type falls under the third case.
8. A digital video decoding method for decoding an input bit stream including a picture header, the digital video decoding method comprising the steps of: (a) comparing an indicator field of a previous frame and an indicator field of a current frame in the input bit stream, each indicator field being a predetermined field for indicating whether a coding type has been changed; (b) estimating a change in the coding type by estimating a bit value, which has been used in a bitwise logical operation, based on the fact that the value of the indicator field of the current frame is obtained by performing the predetermined bitwise logical operation with respect to the value of the indicator field of the previous frame and the bit value, which is determined according to the estimated change in the coding type; and (c) determining a decoding type for the current frame referring to a corresponding field of the previous frame, based on the estimated change in the coding type.
9. The digital video decoding method of claim 8 , wherein the indicator field is a group-of-block frame identifier (GFID) field which is defined by an H.263 standard.
10. The digital video decoding method of claim 8 , further comprising the step of using the picture header information of a next frame as the picture header information of the current frame, when the picture header information of the current frame is lost in a case where it is identified that an update full extended picture type (UFEP) field of the current frame is set to 001 and when the value of the indicator field of the current frame is the same as that of the next frame.
11. A digital video coding device for encoding input video frames and outputting a bit stream including picture headers, the digital video coding device comprising: a coding type change identification unit for identifying how a coding type is changed between a previous frame and a current frame and outputting bits for indicating a state of the change; and an indicator field determination unit for performing a predetermined bitwise logical operation with respect to a value of an indicator field of the previous frame and the bits, which are determined according to the identified change in the coding type, and determining a result value of the logical operation as a value of an indicator field of the current frame, each indicator field being a predetermined field for indicating whether the coding type has been changed.
12. The digital video coding device of claim 11 , wherein the indicator field is a group-of-block frame identifier (GFID) field which is defined by an H.263 standard.
13. The digital video coding device of claim 11 , wherein the bitwise logical operation is an exclusive OR operation.
14. The digital video coding device of claim 11 , wherein the bits have a different value according to a first case in which a rounding type changes, a second case in which an intra frame is changed into an inter frame or an inter frame is changed into an intra frame, and a third case in which a coding type change other than the former two cases occurs.
15. The digital video coding device of claim 14 , wherein the third case includes a change in an annex which is a detailed appendix defining an optional coding method in view of a digital video coding related standard.
16. The digital video coding device of claim 15 , further comprising an update full extended picture type (UFEP) field determination unit for setting UFEP fields, which are defined by an H.263 standard, to 001 , with respect to the current frame, in which the change in the coding type occurs, and a next frame, when bits indicating that the change in the coding type falls under the third case, is received.
17. The digital video coding device of claim 14 , further comprising an update full extended picture type (UFEP) field determination unit for setting UFEP fields, which are defined by an H.263 standard, to 001 , with respect to the current frame, in which the change in the coding type occurs, and a next frame, when bits indicating that the change in the coding type falls under the third case, is received.
18. A digital video decoding device for decoding an input bit stream including a picture header, the digital video decoding method comprising: a comparator for comparing an indicator field of a previous frame and an indicator field of a current frame in the input bit stream, each indicator field being a predetermined field for indicating whether a coding type has been changed; a coding type change estimator for estimating the change in the coding type by estimating a bit value, which has been used in a bitwise logical operation, based on the fact that the value of the indicator field of the current frame is obtained by performing the predetermined bitwise logical operation with respect to the value of the indicator field of the previous frame and the bit value, which is determined according to the estimated change in the coding type, and for outputting a coding type change indication signal for indicating the estimated change in the coding type; and a decoding type determination unit for determining a decoding type for the current frame referring to a corresponding field of the previous frame, based on the estimated change in the coding type.
19. The digital video decoding device of claim 18 , wherein the indicator field is a group-of-block frame identifier (GFID) field which is defined by an H.263 standard.
20. The digital video decoding device of claim 18 , further comprising: an update full extended type (UFEP) field state identification unit for identifying whether an UFEP field of the current frame is set to 001 and outputting an UFEP identification signal for indicating that the UFEP field is set to 001 , when the picture header information of the current frame is lost, in a case where the coding type change indication signal indicates a change in an annex which is a detailed appendix defining an optional coding method in view of a digital video coding related standard; and a current picture header determination unit for outputting a current picture header indication signal for indicating that the picture header information of a next frame is the picture header information of the current frame, in response to the UFEP identification signal, when the value of the indicator field of the current frame is the same as that of the next frame.
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March 31, 2000
May 7, 2002
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